The goal of our proposed research is to understand the mechanisms involved in the generation of complex sounds, which can be found in the songs of many birds, and to unveil the role of the peripheral system in this process. As an initial step, the physiological parameters (electromyograms of syringeal muscles, tracheal and bronchial airflow data) will be described for the full range of acoustic characteristics in the songs of three species, zebra finch, brown-headed cowbird and European starling. Based on these data, models of sound generation in the avian vocal organ, the syrinx, will be developed and experimentally tested in order to elucidate the physical processes underlying this acoustic versatility. Following this integrated approach, the focus will be on nontrivial acoustic features, which are present in the songs of the selected species. Electromyographic recordings of syringeal muscles in these birds will reveal the degree to which neural instructions can account for the generation of complex sounds. We will test the hypotheses that complex sounds arise from acoustic interaction between the two sound sources of the syrinx and from feedback pressure onto labial vibration by a combination of modeling and experimental tests. The proposed research is a comprehensive integrative approach to illuminate the peripheral physical mechanisms of birdsong production. The results will inform about the degree to which the peripheral system can give rise to complex acoustic behavior without parallel complexity in the neural control. This research will provide valuable insight into the link between neural control, peripheral interactions and learned vocal behavior in birds and, therefore, explore issues that are also of significance for our understanding of human speech production and motor control. [unreadable] [unreadable]